Circuit controlling thermostat and mount therefor



Patented-- July 6, l 1937 CIRCUIT ooN'rRoLLING' .THERMOSTAT AND MoyUN'r THEREFOR n Harry Campbell Grant, Jr., New York, N. Y., as-

signor to Walter Kidde & Company, Inc., New York, N. Y., a corporation of New York Application January 12, 1933, Serial No. 651,313

1 Claim.

This invention relates generally to circuit controlling thermostats of the type which is commonly used to control the opening and closing o electrical circuits such as are employed, for example, in electrically operated re detecting, repreventing and re extinguishing systems.

More specically the present invention relates to normally open-circuited thermostats of the type which are connected to bridge parallel cir- 0 cuit wires, whereby operation of any one of the parallel thermostats closes the circuit through the parallel wires and thereby effects a suitable signal or other operationl Prior to this invention such thermostats have 15 been constructed to be bridged across continuous parallel' wires of an electrical circuit.

Prior constructions have had a most serious drawback in that the removal of a thermostat from its position in parallel with the continuous circuit Wires (with the undesirable removal of its function) has no positive effect on the electrical circuit, so that no signal of any kind is rendered at a central station to indicate such removal. It will of course be apparent that such removal o might be either out of pure mischief or out of criminal design to prevent the turning in of a fire signal, or it might be an entirely proper removal of a used or short-circuited thermostat with an unfulfilled or forgotten intention to substitute a new thermostat, or it might be a constructive removal as by the breaking of a Wire from the thermostat to one of the parallel circuit wires.

The present invention solves this difficulty by providing a thermostat constructed so thatthe parallel circuit wires must be run in sections between parallel thermostats and so that the sections of the circuit wires are bridged by the thermostat when it is in its proper position.

With this construction removal .of a thermostat from its proper position, for any reason Whatever, breaks the electrical circuit and enables a suitable'open-circuit signal to be rendered at a .central station.

The present invention contemplates the provision of amounting base for the thermostat constructed so that the circuit wires are connectible in sections to the mounting box and so that the gaps in the circuit wires are bridged by the thermostat when mounted on its mounting base, the mounting base being preferably constructed so that the circuit wires must be run in sections between mounting bases and so that it is relatively more difficult to bridge the gaps in the circuit wires resulting from the removal of a thermostat by other means than it is by the substitution of a new thermostat.

It is accordingly an object of the present invention to provide a thermostat for'connection in an electrical circuit having parallel circuit wires so constructed and arranged that the circuit wires must be run in sections between parallel thermostats and so that the sections of the circuit wires are bridged by the thermostat when it -is in its proper position in the electrical circuit.

It is another object of thepresent invention f to provide a thermostat for connection in an electrical circuit having parallel cir-cuit wires, so constructed and arranged that removal of the thermostat from the electrical'circuit will break the circuit and enable a suitable open-circuit signal to be rendered at a central station.

A still further object of the invention is to provide a thermostat and mounting base therefor for connection in an electrical'circuit, constructe'd and arranged so that a circuit wire is connectible in sections to the mounting base and so that the gap in the circuit wire is bridged by the thermostat when mounted on the base.

Still another object of the invention is to provide a thermostat and mounting base therefor for connection in an electrical circuit, constructed and arranged so that a circuit wire must be connected in sections to the mounting base, and so thatV it is relatively more difficult to bridge a gap in the circuit wire resulting from removal of the thermostat by other means than it is by the substitution of a new thermostat.

Still another object of the invention is to provide a mounting base capable of use with a thermostat in accordance with this invention.

yThese and other objects of the invention, not specifically enumerated above, will be apparent as the invention is described in greater detail in connection with the accompanying drawings, wherein:

Figure 1 is a View, mostly all'in section, of a thermostat and its mounting base shown in a position against the ceiling of a structure, the section being taken on line l-I of Figure 3 and looking in the direction of the arrows.

Figure 2 is a plan view of the thermostat assembly of Figure 1, looking at the face thereof which is mounted neXt to the mounting base.

Figure 3 is a plan view of the mounting base of Figure l, with the thermostat assembly removed, looking at the face thereof which receives the thermostat assembly.

Figure 4 is a view in section of the mounting Cil base, taken on line 4-4 of Figure 3 and looking in the direction of the arrows.

Figure 5 is a view in section of the thermostat assembly, taken on line 5--5 of Figure 2, the thermostat element itself being shown only partly in section.

Figure 6 is a view in elevation of ya suitable thermostat element for the thermostat assembly.

Figure '7 is a plan view of a bridging piece adapted to be connected to a terminal of the thermostat.'

vFigure 8 lis a view in elevation of one of the connector pieces inserted in the mounting base.

Figure 9 is a perspective view of the thermostat element of Figure 6 shaped as it appears in the assembled device.

Figure 10 is a view in section, on an enlarged scale, through the thermostat lelement of Figure 6.

In Figure 1 of the drawings I represents a mounting base, or more specifically a mounting box, of electrically insulating material, to whichl is secured a thermostat assembly '2, the mounting box being itself secured to any suitable structure 3. The mounting box is suitably chambered, as at 4, and is provided with secondary electrically conductive terminals 5, to which the thermostat assembly is secured by means of screws 6.

Referring now to Figures 3 and 4 which show the details of construction of the mounting box I, the reference numeral 4 represents a chamber into which the sections of the circuit wires are inserted for connection with the electrically conductive primary terminals "I, which are electrically connected to the secondary terminals 5 in a manner to be described. Figure 3 shows two sections 8 and 8 of one of the circuit wires to which the mounting box is adapted for connection. Each ofi the four primary terminals 1 consists of a screw threaded insert, as shown in Figure 4, while each of the four secondary terminals 5 also consists of a screw threaded insert, as

shown in Figure 1. the secondary terminals are electrically connected in pairs, by electrically conductive connecting pieces I0 and I-l, each pair so connected consisting of one primary terminal and one secondary terminal.

The mounting box is preferably made of a suitable molded electrically. insulating-composition, and eachpair of terminals is preferably made as a unit to be inserted in the mold at the time of molding the mounting box. Such a unit, com- \prising one primary terminal 1, one secondary f terminal 5, and a connecting piece I 0 (or I I for the longer connecting piece), is shown in Figure 8.

As shown in Figure 4, the secondary terminals 5 lie relatively closer to the open face I2 of the mounting box, While the primary terminals I are each recessed within a surface I3.

As shown in Figure 3 each recess in a surface I3 comprises a circular portion I4 and a tangential portion I5 extending to the edge of the surv,face I3, the purpose of this construction being to permit an uncovered portion of a circuit wire to be inserted in the Wire directing channel I5 and coiled in the circular recess .I4, so that it can then be secured in position by a washer-head screw, one of which is shown at I6, electrical connection being thereby established from a section of a circuit wire, through a washerhead screw I6, a primary terminal "I, a connecting piece IU or II, to a secondary terminal 5.

While Figure 3 shows only two Sections of one The primary terminals and circuit wire connected to two of the primary terminals, it will be seen that the opening II through the wall of the mounting box provides for the entry of two section; of another circuit wire, which sections can be connected to the remaining primary terminals in the same manner. W'hen all of the circuit wire sections are connected, it will be apparent that each secondary terminal 5 is electrically connected to a section\ of circuit wire, and it will be further apparent that electrically bridging each of the associated pairs of secondary terminals 5 will effect closing of the gaps existing between the two sections of each circuit wire,

The manner in which bridging of a pair of secondary terminals of the mounting box is accomplished will now be described with particular reference to Figures 2 and 5, in which I8 is a base of electrically insulating material suitably chambered for the reception of the thermostatelement I8. Figure 6 gives a somewhat better view of the thermostat element, the details of construction of which form no part of the present invention; While Figure 9 shows the shape which the thermostat element assumes in the assembled device. For the purpose of theV present description itis suflicient to note thatthe Ithermostat element is provided with two electrically separated terminals 20, suitably perforated at ZI, the thermostat element being designed to close a circuit between the terminals I20. In other respects the construction of the thermostat elementmay be as desired. Thus, for example, the construction may be the same as that shown in Letters Patent of the United States No. 1,274,248. Such a thermostat elment'is shown, by way of example, in section in Figure 10. For the purpose of bridging the thermostat terminals 28 across the secondary terminals 5 of the mounting box I bridging pieces 22, shown in Figure '7, are employed; each bridging piece being provided with suitable perforations 23 and 28, the purpose of which will be described. l'

The base I8 (Figure 5) is provided with screwthreaded recesses 24, with a shallow recess I8 conforming to the outline of the thermostat elementv I9, and with slots 25, so that the thermostat element I9 can be assembled into the recess I8 in the base I8 with its terminals 20 passed through the slots 25 and bent over to lie in close contact with the opposite upper surface of the base I 8, the perforations 2I in the terminals 20 being arranged to coincide with the screw-threaded recesses 24 in the base I3. As will be seen in Figure 2, recesses 26 are provided in the upper surface of the base I8 conforming to the outline ofthe bridging pieces 22 and deep enough to receive said bridging pieces. When the thermostat element I9 has been assembled into the base I8 as already described, a bridging piece 22 is placed in each recess 26 over a terminal 20 and in direct contact therewith. The perforations 23 of the bridging pieces are arranged to coincide with the perforations 2| of the thermostat terminals 2li, so that both the thermostat and/the bridging pieces may be held in position by the screws 21. It should be noted that each bridging piece is provided with perforations 28 which are so arranged that they coincide with suitable passages 28 in the base I8 and with the screw-threaded recesses in the secondary terminals 5 of Ithe mounting box I.

The manner in which the thermostat assembly is connected to the mounting box I'will best be understood with reference to Figures 2 and 3, the

. vthermostat assembly as shown in Figure 2 being first rotated through an angle of 90 and then turned over so that the bridging pieces 22 face downwardly with respect to the surface of the drawings. 'The thermostat assembly is then applied to the open face of thevmounting box I as illustrated inFigure 3, being received within the recess shown more clearly in Figure 4, at which time, byreason of the specific construction already described, the perforations 28 in the bridging piecesl22 of the thermostat assembly and the corresponding perforations 28' in the base I8 will overlie and coincide with the screw-threaded recesses in the secondary terminals 5 of the mounting box I.

,The screws 6, shown in Figure 1, are then passed through the holes 28 in the bridging pieces and the holes 28 in the base I8 and are threaded into the screw-threaded recesses in the secondary terminals 5 of the mounting box I so as to hold the thermostat assembly securely'to the mounting box. Electrical contact will then be established between the bridging pieces 22 and the secondary terminals 5 by reason of the surface contact maintained therebetween by the screws 6; andYV not only will each of the bridging pieces 22 be bridged across a pair of secondary terminals 5, thus connecting the isolated sections of the parallel circuit wires already referred to, but the thermostat element I9 of the thermostat assembly( will be bridged across the parallel circuit wires.

Referring to Figure 10, which shows the details of construction of one form of thermostat element which may beemployed, by way of example, in conjunction with the present invention, the thermostatic circuit closing element proper is enclosed in a casing which is formed directly of the two circuit terminals, these terminals being formed as two discs 3D and 3I havingintegral upturned tabs 20 for connection to the base I8 of the thermostat assembly, the disc 3l being somewhat smaller in diameter than the disc 30 so that when laid upon the disc 30, its peripheral edge will be spaced froma flange 32 upon the disc 3B.

Each of the terminal discs 3U and 3| preferably has annular corrugations pressed therein to increase the heat absorbing surface, and the discs also have nesting central depressions 33 and 34, the depression 33 being adapted to receive a disc 35 of easily fusible material, which constitutes the thermostatic circuit closing element proper.

The opposed faces of the terminal discs 30 and- 3I are insulated from each other, preferably by a thin disc 3B of Varnished silk or other suitable insulating material perforated at 3'! over the fusible disc 35, the disc 36 thus insulating the fusible disc also from the disc 3Ibut permitting the fusible material of the disc 35 to spread through the perforations 3l yupon fusing, to bridge the terminals 30 and 3|. The insulating disc 36 is preferably of such diameter that it fits closely within the space bounded by the flange -32 of the disc 30.

Each ofkthe discs 30 and 3l has a plane-mar-l ginal portion outside the corrugations, the purpose of this marginal portion being to provide a nat clamping surface upon each disc, adaptedV to cooperate with the corresponding surface upon the other disc to insure a tight joint about the .edges when the discs are clamped together to form a closed'casing. In order to maintain the insulating disc substantially in one plane and to prevent injury to this disc by excessive pressure ably register so that a slight corrugating of the material of the disc 36 will usually be effected by the clamping pressure exerted in clamping the parts into their final relation.

The opposed faces of the discs 30 and 3l are insulated from each other by the insulating disc 36. The edge of the disc 3I is preferably insulated from the flange 32 of the disc 30 by an air gap, and in order therefore to insure maintenance of the edge of the disc 3l in spaced relation to the flange 32 of the disc 30, an annular insulating piece 39 is provided which has an outer diameter corresponding to the diameter of the space within the flange 32 and an inner diameter corresponding to the diameter of the outer borrugation of the series of corrugationsv on the disc 3|. Thus, when the parts are assembled, the ring 39 will center the disc 3l in spaced relation to the flange 32 of the disc 30. The ring 39 also insulates the overturned flange 32 of the disc 30 from the disc 3|. In order to insure the insulation of the tab 20 of the disc 3I from the disc 30 when the parts are clamped together, the flange 32 is interrupted at a point opposite said tab 20, proper spacing of the elements being provided. Of course, the flange 32 is also interrupted at the point where the tab 20 of the disc 3U projects, soI that proper clamping may be effected.

In order to insure quick and positive operation of the device, it is important that the parts of the V terminals to be bridged shall be as close together as possible, and, moreover, that they'preferably exert a pressure upon the fusible disc'35 to cause it to flow through the perforations 31 of the insulating disc 36 as soon as it begins to fuse. To this end the terminal discs 30 and 3I are preferably so tensioned, either before or during the clamping operation by which they are joined to form a casing, that the nesting central depressions 33 and 34 of the ltwo discs tend to clamp between them the fusible disc 35 and the opposed portion of the insulating disc 36, having therein the perforations 31.

The above completes the description of the thermostat element so far as it concerns the present invention, it being kept in mind that the del With further reference to Figure 4, it should be noted that the holes 29 are provided for screws or bolts to hold the mounting box in any desired position.

It should also be noted that with the construction of the mounting box as described, once the mounting box is connected to the circuit wires, it is relatively more diicult to bridge the gaps in the circuit Wires left by the removal of a thermostat by any other means than by the simple substitution of a new thermostat for a used one, the invention thus facilitating proper servicing of the apparatus.

From the foregoing description it will be seen that my invention embodies the important objects pointed out at the beginning, providing, as it does, a thermostat and mounting base therefor, in which circuit wires must be run in sections to and between mounting bases; in which mounting of a thermostat on its base completes a circuit through the sections of wire; in which, conversely, removal of a thermostat from its mounting base breaks a circuitfthrough said sections and enables a suitable signal to be rendered at a control station; in which, in fact, even loosening of a thermostat suiiciently to break the circuit, as by the loosening of a single holding screw, at one point, is sufcient to turn in a trouble signal at the central station; and in which, finally, the thermostat can be removed and re placed 'without disturbing any circuit wires.

However, while the invention has been described inconnection with the details of construction shown in the accompanying drawings, it will be apparent to those skilled in the art that the invention can be embodied in other forms of construction without departure from the spirit and scope of the invention, and for this reasoirI do not wish to be strictly limited to the disclosure but rather to the scope of the appended claim.

A thermostat and mounting base assembly for connection in an electrical circuit comprising a mounting base provided with two pairs of spaced terminals having screw threaded recesses therein, a thermostat provided with a pair of terminals, each having a pair of spaced apertures adapted to coincide with the screw threaded recesses of a pair of mounting base terminals when the thermostat is positioned on the mounting base, and a plurality of screwthreaded members adapted to pass through said apertures and engage in said screw threaded recesses and serving to mount the thermostat on the mounting base and to effect electrical connection between the corresponding thermostat and mounting base terminals.

HARRY CAMPBELL GRANT, JR. 

